Generally, a sun light battery using an amorphous silicon or the like has a low reverse blocking voltage, and in the case where some elements come into shade in a module in which plural elements are implemented, the electro-motive forces generated by the unshaded elements are applied to the shaded elements in a reverse polarity, and these elements are likely to be destroyed. In order to prevent this destruction, a monocrystalline silicon diode is soldered onto the sun light battery substrate as a protection diode.
An example of a conventional device of such construction is shown in FIG. 1. The reference numeral 1 designates a conductive substrate. The numeral 2 designates a first conductivity type, for example, n type amorphous silicon semiconductor. The numeral 3 designates an intrinsic amorphous silicon semiconductor. The reference numeral 4 designates a second conductivity type, for example, p type amorphous silicon semiconductor. The numeral 5 designates a transparent conductive film. The numeral 6 designates a metal current collecting electrode. The numeral 7 designates a metal electrode for connection purposes provided at an outer region of the substrate 1. The numeral 8 designates a second conductivity type crystalline silicon semiconductor. The numeral 9 designates a first conductivity type crystalline silicon semiconductor. The numeral 10 designates a connecting wire for the sun battery element. The numeral 11 designates a connecting wire for the protection diode.
This sun light battery device is manufactured as follows:
Amorphous silicon semiconductor layers 2, 3, 4 are deposited on the conductive substrate 1, the transparent conductive film 5 is vapor-plated thereon, and the metal current collecting electrode 6 and the metal electrtode 7 are vapor-plated on the film 5 and the substrate 1, respectively, to produce a sun battery element. Thereafter, a diode comprising the crystalline silicon semiconductor 8 having the same coductivity type as that of the amorphous silicon semiconductor 4 and the crystalline silicon semiconductor 9 having the same conductivity type as that of the amorphours silicon semiconductor 2 is soldered onto the substrate electrode 7 on the substrate 1. This diode is connected to the sun light battery element by the sun battery element connecting wire 10 and the protection diode connecting wire 11. Thus, the device has a connection as shown in FIG. 2, whereby current-voltage characteristics shown in FIG. 3 are obtained.
In the conventional sun light battery of such a construction, it is necessary to solder a small silicon diode onto a substrate, and in this soldering there is likely to occur a short-circuiting because of the small size of the diode element. Accordingly, it takes a long time for the construction of this device, and the reliability thereof is low.
Another prior art sun light battery is disclosed in Japanese Laid-Open Patent Specification No. 57-122580. In this device, a sun battery element is connected with a diode provided with an adjacent sun battery element in reverse parallel relation, and a series connection of these parallel circuits is realized.